Fiber optic cables are widely used to transmit light signals for high speed data transmission. A fiber optic cable typically includes: (1) an optical fiber or optical fibers; (2) a buffer or buffers that surrounds the fiber or fibers; (3) a strength layer that surrounds the buffer or buffers; and (4) an outer jacket. Optical fibers function to carry optical signals. A typical optical fiber includes an inner core surrounded by a cladding that is covered by a coating. Buffers (e.g., loose or tight buffer tubes) typically function to surround and protect coated optical fibers. Strength layers add mechanical strength to fiber optic cables to protect the internal optical fibers against stresses applied to the cables during installation and thereafter. Example strength layers include aramid yarn, steel and epoxy reinforced glass roving. Outer jackets provide protection against damage caused by crushing, abrasions, and other physical damage. Outer jackets also provide protection against chemical damage (e.g., ozone, alkali, acids).
Fiber optic cable connection systems are used to facilitate connecting and disconnecting fiber optic cables in the field without requiring a splice. A typical fiber optic cable connection system for interconnecting two fiber optic cables includes fiber optic connectors mounted at the ends of the fiber optic cables, and an adapter for mechanically and optically coupling the fiber optic connectors together. Fiber optic connectors generally include ferrules that support the ends of the optical fibers of the fiber optic cables. The end faces of the ferrules are typically polished and are often angled. The adapter includes co-axially aligned ports (i.e., receptacles) for receiving the fiber optic connectors desired to be interconnected. The adapter generally includes an internal split sleeve that receives and aligns the ferrules of the fiber optic connectors when the connectors are inserted within the ports of the adapter. With the ferrules and their associated fibers aligned within the sleeve of the adapter, a fiber optic signal can pass from one fiber to the next creating an optical interface. The adapter also typically has a mechanical fastening arrangement (e.g., a snap-fit arrangement) for mechanically retaining the fiber optic connectors within the adapter.
FIGS. 23 through 26 show a prior art SC style adapter 320 that is frequently used in fiber optic telecommunications systems. The SC style adapter 320 includes a housing 321 having an outer portion 322 defining first and second oppositely positioned ports 324, 326. Resilient fingers 328 are provided on the outer portion 322 for use in retaining the adapter 320 within a mounting opening (e.g., an opening within a panel) by a snap fit connection. Keying slots 323 are provided on the outer portion 322 to ensure proper rotational alignment of the adapter 320 to the fiber optic connectors which may be positioned within the ports 324, 326. The housing 321 also includes an inner portion 330 positioned within the outer portion 322. The inner portion 330 includes a cylindrical split sleeve holder 332 in which a split sleeve 334 is mounted. The split sleeve 334 has a first end 336 accessible from the first port 324 and a second end 338 accessible from the second port 326. The inner portion 330 also includes a first pair of resilient latches 340 positioned at the first port 324 and a second pair of resilient latches 342 positioned at the second port 326.
FIGS. 5 and 6 show a prior art SC style fiber optic connector 422 that is compatible with the adapter 320. The connector 422 includes a connector body 424 in which a ferrule assembly is mounted. The connector body 424 includes a first end 426 positioned opposite from a second end 428. The first end 426 provides a connector interface at which a ferrule 430 of the ferrule assembly is supported. Adjacent the first end 426, the connector body 424 includes retention shoulders 432 that are engaged by the resilient latches 340 of the adapter 320 when the connector 422 is inserted in the first port 324 of the adapter 320, or that are engaged by the resilient latches 342 when the connector 422 is inserted in the second port 326 of the adapter 320. The latches 340, 342 function to retain SC connectors the within their respective ports 324, 326. The second end 428 of the connector body 424 is adapted to receive a fiber optic cable 450 having a fiber 453 that terminates in the ferrule 430. A resilient boot 452 can be positioned at the second end 428 of the connector body 424 to provide bend radius protection at the interface between the connector body 424 and the fiber optic cable 450.
The connector 422 also includes a retractable release sleeve 434 that mounts over the connector body 424. The release sleeve 434 can be slid back and forth relative to the connector body 424 through a limited range of movement that extends in a direction along a longitudinal axis 454 of the connector 422. The release sleeve 434 includes release ramps 436 that are used to disengage the latches 340, 342 from the retention shoulders 432 when it is desired to remove the connector 422 from a given one of the ports 324, 326. For example, by pulling back (i.e., in a direction toward the second end 428 of the connector body 424) on the retention sleeve 434 while the connector 422 is mounted in a given port 324, 326, the release ramps 436 force the corresponding latches 340, 342 apart from one another a sufficient distance to disengage the latches 340, 342 from the retention shoulders 432 so that the connector 422 can be removed from the port 324, 326. The release sleeve 434 includes a keying rail 435 that fits within either one of the keying slots 323 of the outer portion 322 of the housing 321 to ensure proper rotational alignment of the connector 422 within the adapter 320. When two of the connectors 422 are latched, one each within the ports 324, 326 of the adapter 320, the ferrules 430 of the connectors 422 fit within the first and second ends 336, 338 of the split sleeve 334 and are thereby held in co-axial alignment with one another. Further details regarding SC type fiber optic connectors are disclosed at U.S. Pat. No. 5,317,663, that is hereby incorporated by reference in its entirety.
As shown in FIGS. 1 through 4, when coupled together in a functional configuration, two of the connectors 422 and the adapter 320 provide the optical interface protection from contamination. In particular, the overlapping fit of the ports 324, 326 of the housing 321 around the connectors 422 provide a first layer of protection to the optical interface. In addition, the fit of the cylindrical split sleeve holder 332 and the split sleeve 334 around the ferrules 430 provides a second layer of protection. When either of the connectors 422 is disconnected from the adapter 320, the configuration of FIGS. 1 through 4 is split into the lone connector 422, shown in FIGS. 5 and 6, and the adapter 320 with the remaining connector 422 assembled, as illustrated in FIGS. 27 and 28. This leaves the disconnected optical interface exposed to contamination at two locations. The first location is around the ferrule 430 on the lone connector 422. The second location is around and in the split sleeve holder 332 within the open port 324 or 326 of the adapter 320 (with the remaining connector 422 assembled). The optical interface is sensitive to contamination. If the optical interface is contaminated, the fiber optic signal connection may be disrupted upon reconnection.
When two of the connectors 422 and the adapter 320 are coupled together, in a functional configuration, as shown in FIGS. 1 through 4, the fiber optic signal, if present, is contained within the fiber optic cable 450, the connectors 422, and the adapter 320. When a fiber optic signal is transmitted through the fiber optic cable 450 terminated only by the connector 422, as shown in FIGS. 5 and 6, the signal will not be contained and will be emitted as a beam into the environment. Likewise, when a fiber optic signal is transmitted through the fiber optic cable 450 terminated only by the connector 422 assembled to the adapter 320, as illustrated in FIGS. 27 and 28, the signal will not be contained and will be emitted as a beam into the environment. Beam emitting configurations, such as those illustrated in FIGS. 5, 6, 27, and 28, may occur during the construction of a new fiber optic network, when various connections are being established; during testing and diagnosis of an existing fiber optic network, when connections and disconnections are being performed; within an operational fiber optic network, with provisions for expansion that include unused connections; and other instances. When high power signals (e.g., above 0.25 Watt) are involved, light emitted from the fiber optic network can be a safety concern.
A common practice for testing and diagnosing fiber optic connections and networks involves transmitting visible light through the fiber optic cable 450. In certain cases, where only non-visible light is normally used within a cable 450, a low power visible light source replaces the non-visible light source. Upon seeing visible light at the endpoint of a series of connections, the continuity of the optical circuit is assured. Intermediate connections can be disconnected to visually verify the continuity up to that point. A typical opaque dust cap or dust plug prevents visual continuity detection when properly installed on a corresponding connector 422 or adapter 320.
Temporarily removing the dust cap or dust plug allows visual continuity detection to proceed. Transparent and translucent dust caps and dust plugs have been devised that allow visual continuity testing to occur with the dust cap or dust plug installed on the corresponding connector 422 or adapter 320. Certain optical circuits employ high power (above 0.25 Watt) laser signals in the visible and non-visible spectrum.
Attempting visual continuity detection may be unsafe and result in eye damage when high power signals are involved and the dust cap or the dust plug has been removed. Furthermore, transparent and translucent dust caps and dust plugs may also be unsafe when high power signals are involved. There is a need for a dust cap and a dust plug that allow safe, visual continuity detection to occur with the dust cap and the dust plug installed on the corresponding connector 422 and adapter 320. Furthermore, the dust cap and the dust plug need to provide protection from any high power signal which may be present in the cable 450 terminated by the connector 422 and the dust cap or the adapter 320 and the dust plug.